Open coil electric heater



Jan. 12, '1960 A. w. HACKMAN OPEN COIL ELECTRIC HEATER Filed March 26, 1957 3 Sheets-Sheet 1 6 34 a 4 7 2 J 9 M1 4 a 3 a 4 I .\Z d M 2 -u 4 4 4 p 4 M k 4 a A 10 m bw MW 1 w 4 MW MM WJV 0 v 9 4 a a 4 4 4 a J M I 4. 6 2 H l a u w I a 4 4 A 2;; w MW m 552 5 pw m I m MU y 1 f4 4 q 9 W 00 4 1 4 4 (1:14 4 w 4 4 4 4 M W 2 6 4 w IN V EN TOR. 6/2205 71X 75 000726224 BY :1 W m 672 7 Jan. 12, 1960 A. w. HACKMAN OPEN con. ELECTRIC HEATER 3 Sheets-Sheet 2 Filed March 26, 1957 IN V EN TOR. Yfl 7767011 7IZCZZZ/ Jan. 12, 1960 w, HACKMAN 2,921,172

OPEN COIL ELECTRIC HEATER Filed March 26, 1957 3 Sheets-Sheet 3 11 I n 1 s nn IN V EN TOR. 222045; w ffiaakzzzazz/ United States Patent 2,921,172 OPEN COIL ELECTRIC HEATER Amos W. Hackman, Kirkland, Ill., assignor to Iuttle Electric Products, Inc., Kirkland, 111., a corporation of Illinois Application March 26, 1957, Serial No. 648,659

4 Claims. (Cl.21919),

This invention relates to open coil heating units of the type, in which a long helical coil of resistance wire is supported in an open or exposed manner by a grille or lattice type metal framehaving spaced apart electrical insulators, through which the resistance coil extends, the invention having reference more particularly to the electricalinsulating of such units.

Such heating units are commonly used in appliances, such for example as clothes dryers and the like, to heat air by circulation thereof through the open coil heater, and as, the appliances in which these heating units are used are generally made of conductive materials, it is important that there be no current leakage from the heating unit which might cause shock to the operator of the appliance.

Inasmuch as the frames of such heating units are of metal, it is necessary to insulate the resistance coil electrically therefrom and, as such heaters are operated at high temperatures, insulators of ceramic material are employed for the purpose and are depended upon to safeguard the appliance with which the heater is used, against communication of any current thereto from the heating resistance.

Such insulators, however, have the characteristic that when they are highly heated, as they oftentimes are in heating units of the type to-which the invention pertains, they acquire a slight surface conductivity which is likely to permit sufficient current leakage to cause shock to the operator or attendant of the appliance unless the surface distance from the place or places of contact ofthe resistance coil with the insulator to the nearest metal part to. which the insulator is secured is suflicient to become a bar to. any such leakage, and great difliculty has been experienced heretofore in providing a satisfactory ceramic insulator with sufficient surface distance to preclude such leakage.

Flat disk type insulators which were commonly employed with a central opening therethrough to accommodate the resistance coil and with a peripheral formation such, for example, as a V-edge for interlocking; with encircling or partially encircling metal parts of the frame for securing the insulator thereto, could not be provided with sufiicient surface distance to preclude current leakage without making the insulator objectionably large, and

tubular insulators were employed which were provided midway between their ends with an annular V-edged rib therearound for interlocking with the encircling or partially'encircling parts of the metal frame and these tubular insulators could be made of such length to satisfactorily avoid current leakage, but it was found that when these tubular. insulators were made of sufficient length to preclude current leakage, they caused over-heating of the portion of the resistance coil therein and premature burn out of the resistance coil on this account.

The principal objects of this invention are, to provide perienced with previous open coil metal frame electric heaters; to provide heating coil insulation which effectively eliminates current leakage; to minimize the size of insulators required to avoid current leakage; to provide suppleinental facilities for added certainty of complete safeguard against shocks to the operator or attendant of the appliance with which the heating unit is used; and to accomplish these improvements with facilities which are readily adaptable to open coil heaters of the present type without material alteration thereof, these and other objects being accomplished as pointed out more particularly hereinafter and as shown in the accompanying drawings, inwhich:

Fig. 1 is a top view of a heater embodying the improvements of this invention;

Fig. 2 is an enlarged end view of one of the resistance coil supporting insulators of Fig. 1, taken on the line 2-2 of Fig. 1, and showing a portion of the insulator support;

Fig. 3 is a sectional view of the insulator and insulatorsupport of Fig. 2 taken on the line 33 thereof;

Fig. 4 is an end view of one of the mounting bracket assemblies of the heater of Fig. 1 taken on the line 44 thereof;

Fig. 5 is an end view of the insulator of the mounting bracket assembly of Fig. 4; Fig. 6 is a sectional view similar to Fig. 3 of a modification of the insulator of Figs. 2 and 3;

Fig. 7 is a top view of another form of heater made in accordance with the present invention;

Fig. 8 is an enlarged view of one of the mounting,

bracket assemblies of Fig. 7, partly in section on the line 88 of Fig. 7;

Fig. 9 is a sectional view of the assembly of Fig. 8.

taken on the line 9-9 thereof;

Fig. 10 is a perspective view of one of the mounting brackets of Fig. 7;

Fig. 11 is an end view of the insulator of the mounting assembly of Fig. 8;

Fig. 12 is a side view of the insulator of Fig. 11;

Fig. 13 is a top view, with an intermediate portion,

clothes dryer showing the application of a heater of the.

present invention thereto; and

Fig. 16 is a view of the clothes dryer of Fig. 15 taken on the line 16-16 thereof.

Referring to the drawings, and particularly to Figs. 1 through 5. thereof, the heater shown therein comprises a long helical coil 20 of resistance wire which extends back and forth through ceramic insulators 21 carried by an open metal frame, which is indicated as a whole by the reference numeral 22 and has a heavy border wire.

bent in a U-shape with two laterally spaced legs 23 connected by a transverse portion 24 thereof at one end of the frame 22.

The transverse portion 24 has a plate 25 secured there-.

to midway of its length to support two terminal stems 26 and 27 to which the opposite ends of the helical resistance coil 20 are connected, as indicated respectively at 28 and 29, and the terminal stems 25 and 27 are car ried' by separate electrical insulators 30 which are secured in spaced apart relation to the plate 25 so that'the.

terminal stems are electrically insulated from one another and from the plate 25.

A series of spaced apart parallel insulator supporting members 371 and, 32 extend crosswisev of the frame. 22

betweenthe legs 23 thereof to laterally spaced parallel lengths 33 of light bar stock that extend lengthwise of the frame 22, the transverse insulator supporting members 31-and, 32 being welded to the bars 33 as indicated 'at34.

- The two end ones 31 of said insulator supporting members are longer-than the intermediate ones'32, and are connected at their opposite ends tothelegs 23, in a manner hereinafter explained, so that the entire assembly of insulator supporting members 31 and 32, and bars 33 and insulators 21 is supported solely by the legs 23 of the border wire and solely by the connection of the ends of the two end'insulator supporting members 31 therewith.

' The insulators 21 which are of ceramiematerial are of short generally tubular form as shown in Figs. .2 and 3; formed with an externaly-shaped'r-ib 35 extending therearound midway betweenthe ends thereof for mounting purposes, and each of the insulator supporting members 31 and 32 is composed of a pair of narrow metal.

the semicircular portions 36 are flat and secured together as for example by spotwelds 37.

The corresponding insulators 21 of all of the supporting members'31 and 32 are inline and each insulator 21 has a central opening:38 therethrough through which the resistance coil 20 is threaded to provide spacedapart parallel lengths thereof with return bends 39 beyond the insulator supporting members 31 as shown in Fig. 1.

Heretofore insulators of the tubular type had a cylindrical opening extending therethrough of only a slightly larger diameter than the outside diameter of the coil 29 and by reason of this cylindricalform of the openingthe resistancecoil could-contact the interior of the insulator throughout substantially the entire length ofthe opening and on this account a long tubular insulator was required for adequate/length of insulator surface from the place of contact of the resistance coil with the interior of the opening to the metal part of the frame which encircled or partially encircled the insulator for supporting the latter in the frame.

Moreover,.because of the cylindrical form of the insulator opening and the cylindrical form of the resistance coil the latter was in such close proximity to the encircling insulator throughout the length of'the opening thereof that the insulator becarhehighly heated and the portion of the resistance therein readily became over prematurely within theheated and would burn out insulators.

It is an important featurev of the present invention that the opening through the insulator is reduced in size midway between the ends thereof so that the resistance coil is held centrally in the opening solely by facilities. occupying only a short portion of the length of the opening midway between the ends thereof, the insula'torjopening at both sides of this midway place being of sufficiently large size so that there not only is no possible contact of the resistance coil with the insulator except at the place midway of the length of the insulator opening but the resistance coil at both sides of this midway place is sutficiently remote from the surrounding wall of the opening that the wall may besaid to be spaced from the coil inpetticoat relation so as to greatly minimize the heating of the insulator and overheating and burn out the resistahce coil.

Thus the length of insulator surface from the place of and are secured together possible contact of the'resistance coil with the insulator to the metal parts which encircle the insulator for supporting the latter on the frame is increased by the length of internal surface of the insulator at each side of the midway place where the resistance coil is supported thereon and a shorter length of insulator may be employed than heretofore with assurance of safeguard against current leakage, and this, as well as the remoteness of the resistance coil from the wall of the insulator opening at each side of the midway place also provides assurance against overheating and burn out of the resistance coil.

For localizing the support of the resistance coil and contact thereof with the insulator at a place midway of the length of the insulator opening, the insulator may be provided with a plurality of circumferentially spaced internal projections 40 as shown in Figs. 2 and 3, three such projections being there shown and these may be narrow axially extending ribs'as shown in Fig. 2 and need be only of such axial length to bridge the space between convolutions of the resistance coil as shown in Fig. 3, and except at the projections 40 the size of the opening 38 is such that the resistance coil 20 is safely spaced from the Wall thereof to avoid any possible contact therewith and provide a substantial air gap therebetween to minimize heating of the insulator. I

Instead of employing a series of projections or ribs 4 s as shown in Figs. 2 and 3 the insulator may be formed as shown in Fig. 6 with an opening of a reduced diameter as indicated at 41 to support and contact the resistance coil only at a place midway of the length of the insulator opening and at opposite sides of the midway place 41,

the insulator opening may be flared outwardly as indicated at 42 to'an enlarged size at each end considerably in excess of the diameterof the resistance coil, thus producing the desired petticoat effect.

For additional assurance of non-conductivity of current from the heating unit to the appliance on which it is mounted, I have also provided the unit with mounting facilities by which the resistance coil supporting portion of the frame of the unit is electrically insulated with certainty from the appliance, and for this purpose the two end insulator supporting members 31 are secured at their opposite ends to the exterior of tubular insulators 43 which have central openings 44 through which the arms 23 of the border wire of the frame extend, and the other insulator supporting members 32 are of shorter length so that they have no connection with the arms 23 and the only connection of the assembly of frame parts 31, 32 and 33 with the border wire of the frame is through-the end insulators of the end members 31.

Obviously the members 32 may be like the members i 31 and provided with insulators 43 at'the opposite ends manner as the insulators 21 are secured to the members 31 and 32, and for this purpose the insulators 43 are mounted on the border wire arms 23, but the construction illustrated and described above is preferred.

The insulators 43 are of ceramic material and are preferably secured to the end members 31 in the same provided with an external V-shaped rib 45 extending therearound midway between the ends of the insulator and the upper and lower strips 31 and 31 of the members 31 are provided with matching opposed semicircular formations 46 which are like the semicircular formations 36 and of V-shape cross section to interlock with the ribs 45 of the insulators 43, and the two strips'31 and 31 are flat and arranged in face to'face engagement and secured to one another, as for example by spot welding, at opposite sides of the insulators 43 so that the latter are permanently secured in place.

Each insulator 43 is straddled by spaced arms 47 of a mounting bracket or plate 48'by which the heating unit is mounted on' the appliancewith which it' is used,

the ends of the arms 47 beingl'ooped around the border wire 23 as shown at 49, the opening between the arms 47 being of such depth that ample clearance is provided ag nt-.72.

5. ond the Pa r end of e ree? member 3 o a e 5113 33? ei e 99th? aid tr ns m m an T e e h s he email be fiat Qr arche transversely or of any other'for'in 'r ui'red fer the particular appli: e 2 whi h used, an

being shown mj'Ei'gsflj and 16 in a clothes dryer n fim'idee form in wh h. a anneal m ve h g t c 'i srsl. war .1 wh c is ap rtur d nd d at52," is mounted to rotate within a closed cylindrical i ggt, ,7 I

rum 5". a d. its/endg me lin cal shell 53 are inou nted withinnn outer casing 54 and an access openings provided, c doior 5 6 for. depositing inand removing fr e ior of the drum 5!) clothes whitliare u hl i b the rot tiq o he u for drying. v v I I The outer casing 54 has one or more air inlet openings through'which air'is suppliedto the interior thereof and the cylindrical shell 53jhas 'an opening 57 therethrough at the top through air suppliable from the interior of the outer casing 54'to' the space between the cylindrical through the perforations 52 shelPS-SandfrGin that spa to the interiorof the dru in SOQ exhaust fari- 58is" connected to the cylindrical shell 53' at'the'bo'ttoifi to exhaust air from the interior of the shell an'tl'the space between the shell 53 and the dru m 50 'is sufficiently separated, as foriexample by partition means 59 extending inwardly from the wall ot the shell 53, into upperand' lower sameness as to cause the air entering'thrdugh t'he 'opning 57 info the upper section to pass into and thr'o'fighlthe drum 50 to the lower section in the exhaus't'operation of'the exh aust fan 58.

A heater such as desefibed above'i's mounted directly abbve the. opening'5 7 as indicated arrow heat the air supplied to theint'erior 'ofthe shell 53andispreferably transversely. arched as" indicated in Fig. 16 to correspond to the cylindrical w'allof'the shellf 4 I The mounting bracket's or' plates 48 may be of any shape or form requiredfor moui' tirigth'e heatingin the appliance with which it is used and for the mounting thereof in the dryer of Figs. and 16 the brackets 48 extend downwardly as indicated hi6; and an out; in was t ej f'raa nd. w th, ot 6 or openings bolts or screws by which the heater is secured to the shell 53 at opposite sides of the opening '57 and held in, a slightly elevated position above the opening 57;

s e ter, bein t he; on-{ i e sh l 5 is 4 to the top wall oftheotfrter cabinet or casing 54 and the latter] is preferably proyided on the underside of t e. top a Ma ner sed hs e elcw wi h a reflector plate 65. overlies the heater 6Q;to reflect; beat down: we d t sr t om. oward-the pen 57..

T e ryer c in she 53; andJVariQus other Parts within the casing 54 are of metal: and assembled in a conyentional mannerwwhich generally permits electrical conductivity from onepart to another, and moreover these. parts. are usually exposed to moisture conditions which promote electrical=cor1ductivity by reason of which it is essential that the resistance coil 20 besafely insulated electrically therefrom, and; the electrical insulation of the mounting brackets 48 fromthe frame of the heating n we s. neid tiaa an efieqi s. a e a d fer. h s tp t pq l .o I t The heaters of Figs, 7' and 13 are of the same C0111, struction as the hea f Fig. 1, except as hereafter explained and, the corresponding parts hereof are indicated, by the same reference numerals asvapplied thereto F g I "In the construction. ohEig. 7, the marginal frame of; Figl l oimittediand the terminal stems 26 and 27 and. their insulators 30 are mounted in a plate 66 which is, adapted to be mounted directly on and supported by tive applica o of Such the l t es er 9 ther ap l a w w h he heater is employed.

Moreover in the Fig. 7 construction, mounting brackets are secured directly to the insulators at the outer ends of the end insulator supporting members 31, these brackets being indicated at 67 and the insulators to which they are secured being indicated at 68.

These insulators 6 8 differ from the corresponding insue lators of Fig. l in the respect that each of the insulators 68 has a slot like opening 69 extending therethrough to accommodate a flat tongue 70 of the mounting bracket 67 by which the bracket is secured thereto.

This mounting bracket 67 is of the same general form as the brackets 48 of Fig. 1 and has a pair of laterally spaced arms 71 and72 with the tongue 70 integral with the arm 71 and projecting therefrom toward the other arm and the latter arm has its outer end folded around the extremity of the tongue 70 as indicated at 73.

Thus before the fold 73 is formed, the tongue 70 may be bent away from the arm and the insulator 68 then slipped onto the tongue 70 after which the tongue 70 is then bent back to the position in which the outer end of the arm 72 is folded around the extremity of the tongue 7Q to lock the bracket 67 on the insulator 68.

' The insulator 68, like the insulators 43 of Fig. 1, has an annular rib 74 therearound by which the insulator 6 8 is secured in opposed semi-circular seats 36 of the upper and lower strips 31 and 31} of the insulator supporting members 31, but the annular rib 74 of the insulators 6 8 of the Fig. 7 construction are preferably provided with diametrically opposed protuberances 75 as shown in Figs. 11 and 12, to engage between outwardly bent portions at the extremities of' the semi-circular portions 46 between which the insulators 68 are interposed.

Thus the insulators 68 are keyed against turning in the seats of the semi-circular portions 46 and as the bracket 67 is oriented in a fixed position with respect to the insulator 68 by reason of the engagement of the flat tongue 70 thereof with the slot like opening 69 of the. insulator 68, the brackets 67 may be held in a fixed supporting relation to the heater of Fig. 7.

In the heater of Fig. 13 Wire members 76 and 77 are,

provided at the opposite ends of the heater for mounting the heater on an'appliance, each said members 76 and 77 having loops 78 at'their opposite ends to accommodate fasteners for that purpose, and the wire member 76 has a plate 79 secured thereto by which the terminal stems 26 and 27 and; their insulators 30 are supported.

The end insulator supporting members 31 of the Fig. 13 heater have insulators 80 secured to their ends in a different manner than the insulators 43 are secured to the members 31 in the Fig. 1 construction, theinsulators 80 being similar to the insulators 68 of the Fig. 7 con-t struction in the respect that the insulators 80 have a slot like opening 81 therethrough to receive therein the outer ends of the two strips 31* and 32 of the members 31 as shown in Fig. 14.

Each insulator 80vhas an annular rib 82 thercaround and the wire member 76 has a pair of brackets 83 secured, thereto and connected to the insulators 80 at the opposite ends of one of the insulator supporting members 7 31 andthe other wire member 77 has a pair of similar brackets 83 thereon and connected to the insulators 8Q at the opposite ends of the other insulator supporting member 31. I

These brackets 83 are composed of two strips 83 and 83', one overlying the other and provided with opposed semi-circular portions 84 engaged around and secured to the respective wire members 76 or 77 and at their other ends these strips 83 and 83 have opposed semi-s circular portions 85 engaging the annular rib 82 of an insulator 80 to secure the latter therebetween.

The strips 83? and 83 are permanently secured toone another, as for example, bywelding and the insulators 80' preferably have diametrical "protuberances'lsdj like those at 75 in Figs. ll and 12, to key the insula'tors80 against turning movement in the seats 85. t

The openings 81, 69 and 44 of the respective insulators 80, 68 and 43 may be like those of the coil receiving insulators 21 in the respect that they are of restricted size at a place midway between the ends thereof con forming to and closely confining the part engaged therein and are of enlarged cross section at opposite sides of that midway place, as indicated by dotted lines at 81 'in Big. 14, and at 69 in Figs. 9 and 11 and at 44 in Fig.'5 to provide such clearance at opposite sides of such midway place that the part engaged in the opening contacts with the insulator only at the midway place of the open ing.

coil is not only safely insulatedfrom the metal frame of the heater by insulators which avoid overheating and burn out of the resistance, but the heater is also provided with insulated mounting means as a part thereof which precludes with certainty any possible current leak age from the heater to the appliance with which it is used.

While I have shown and described my invention in a preferred form, I' am aware that various changes and modifications may be made without departing from the principles of the invention, the scope of which is to be determined by the appended claims.

I claim: g 1. An open coil heater of the class described comprising an electrically conductive frame with portions thereof spaced apart to provide openings through the frame from one side thereof to the other side thereof, a long helical coil of resistance wire which is carried by the frame and arranged circuitously thereon to extend across said Openings of the'frame and is energiza'ble to supply heat, and electrically conductive mounting means by which the frame is securable to a support, the frame having thereon two sets 'of electrical insulators, one set of which is interposed between and electrically insulates the resistance coil from the-frame and the other set of which is interposed between and electrically'insulates the mounting means from the frame and wherein the insulators of both sets are substantially cylindrical bodies of insulating material each peripherally engaged in a metal holder and having an opening extending axially therethrough from end to'end thereof through which a metal part extends for electrical insulation thereof from the metal holder, the axial openings of at least one set of said insulators having elongated enlarged opposite end portions thereof constituting the major portion of the length of the opening and extending oppositely from a narrow midlength expanse of the opening which is locally restricted to hold the metal part therein in a substantially central position of annular spacing from the insulator throughout the length of said elongated enlarged opposite end portions of the opening. t

2. An open coil electric heater of the class described comprising an electrically conductive frame, a long helical coil of resistance wire' 'arranged circuitously on the tors are peripherally secured with opposite end portions With the constructions above described the resistance,

tion of the length of the opening and being defined by insulator portions which are annularly spaced from and skirt the helical coil at a distance therefrom in'petticoatinsulating relation arb'undthe coil througho'utt'helength of the enlarged end portionsfwitheach lof said ,last

mentioned insulator portions being" out or range of contact withthe coil throughout the length of said enlarged end portions and with eachof saidfenlargedendportionsproviding [an annular air chamber around .thecoil for cooling thereof, said annular air chambers being open at their outer, ends for free access of air thereto.

3.7An open coilelectricrheater. oftthe class described comprising (an electrically conductive frame, a,long he1- ical coil of resistance .wire arranged circuitously on the frame, and a pluralityjof spaced apart electrical insulators by which the helical coil is mounted on and elec-- trically insulated. from the frame, said frame having spaced ,apartrnounting portions in which the insulators are peripherally secured with opposite end portions of the insulators projecting correspondingly from the mounting portions at OPPosite-sides thereof, each of said, insulators being provided with, an opening through which the helical coil extends, said openings; being formed with a narrow midlengthportion and enlarged end' portions which are of corresponding length and constitute the major portion of the length of the opening and extend oppositely from the midlength portion,

with 'each insulator contacting the coil at the portion thereof in the midlength portion of the opening to hold the coil centrally inthe enlarged end portions ofzthe opening, each enlarged end portion being; defined by an I insulator portion which is annularly-spaced from and of the insulators projecting from the mounting portions at opposite sides thereof, each of said insulators being provided with an opening through which the helical coil, extends, said openings being formed with a narrow midlength portion and enlarged end portions extending oppositely from said narrow midlength portion, with each insulator contacting'the coil at the portion thereof in skirts the helical coil at a distance therefrom in petticoat-insulating relation around the coil throughout the. length of said'end portion and provides'an' annular air;

chamber around the coil for cooling thereof, each said insulator portion which skirtsthe coil as aforesaid being outof range of contact with the coilthroughout the lengthof said enlarged end portions, 'andsaid air chambers being open at their outer ends for free access of air thereto.m .4.'An open coil electric'hea'ter of the class described comprising an electrically conductive frame, a long hel-. ical coil of resistance wire arranged circuitously onxthe,

frame, and a plurality of spaced apart electrical insulators by which the helical coilis mounted on andelec-- trically insulated from the frame, saidframe having spaced apart mounting portions in which the insulators are peripherally secured with opposite end portions of the insulators projecting from the mounting portions at' opposite sides thereof, each of;said insulators being provided with an opening through which the helical coil extends, said openingsbeing formed with a'narrow mid length portion and enlarged'end portions extending oppositely therefrom, with each insulator contacting the coil at the portion thereof in the midlength portion of the opening to hold the coil centrally in the enlarged end portions ofv the opening, said enlarged end portionsconjointly constituting-the majortp'ortion of the length of the opening and being defined by, insulator portions which are annularly .spaced from andskirt the helical coil at a distance therefromin petticoat-insulating relation throughouttthe length of 'the enlarged end-portions, with each of the insulator portions which skirt the coil as aforesaid being out of range, of. contact with the coil throughout the length of said enlargedend portions, and each of said enlarged end portions providing an annular air chamber around the coil for cooling thereof, said insulator having means about its midlength circumference.

projecting externally for interlocking engagement" with said mounting portions of the frame, and-said annular air chambers being open at their outerends for free access of air thereto;

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Denhard July 7, 1914 Jones July 24, 1917 Whittingham Oct. 29, 1928 Cope Oct. 13, 1931 Pickup Feb. 9, 1932 10 Reimers et al. May 1, 1934 McCormick June 19, 1951 Smith June 29, 1954 Averill et a1. Jan. 10, 1956 Averill Ian. 24, 1956 Norris June 26, 1956 Tuttle July 16, 1957 

